diff --git a/tools/gen_signatures_registry.ml b/tools/gen_signatures_registry.ml
index 96f1dc19..15dd0ad8 100644
--- a/tools/gen_signatures_registry.ml
+++ b/tools/gen_signatures_registry.ml
@@ -77,6 +77,7 @@ let f records =
   List.filter (fun v -> v.number >= 1000_l)
 
 let read_file file = In_channel.with_open_bin file In_channel.input_all
+let file_header = {|...|}
 
 let () =
   let content = read_file "registry.rec" in